This invention relates to track assemblies for sliding closure members, in particular for sliding vehicle doors.
In one known type of sliding closure system used widely for vehicle doors, when closed, the external surface of the door lies flush with the external surface of the surrounding frame. When the closure is opened, its initial movement is generally in a direction perpendicular to the plane of the aperture so that the closure is moved clear of the surrounding frame. The closure is then moved in a direction parallel to the plane of the aperture to allow entry into the aperture.
In order to allow this movement, the closure is supported on a number of track assemblies, one of which includes a support arm mounted in a track by a connection which retains the support arm generally perpendicular to the track during the movement of the closure parallel to the plane of the aperture and permits rotation of the arm about an axis perpendicular to the common plane of the track and arm in one end region of the track to allow the closure to move into and out of the aperture in a direction perpendicular to the plane of the aperture.
Such track assemblies have included at least two sets of bearings, one of which is effective to carry the closure member on the track, the other of which carries the support arm and permits rotation thereof as the closure enters or leaves the aperture.
The construction of such track assemblies is relatively complicated and expensive. As a result, it has become the usual practice to incorporate only one such track assembly in a sliding door assembly, the remaining track assemblies having rigidly connected support arms which travel along a track having arcuate end regions. The end regions of track assemblies of this type project outside the plane of the aperture. Consequently, in vehicles, the track assemblies encroach into the passenger or storage area of the vehicle where they occupy useful space and are susceptible to damage.